The threat of receiving biologically contaminated mail has increased due to the increasing use of terrorist tactics by groups and individuals seeking to further their political agendas. Because virtually everyone who receives mail is subject to such threats, it would be a benefit, particularly to advertisers and companies seeking to send legitimate correspondence, packages and the like to have a mail container with a contaminant indicator that could be used by legitimate individuals and companies which would provide the recipient of mail items with a mechanism for verifying the mail item received does not contain a biological hazard in the form of a loose particulate such as powders, granules, and the like. As used herein the term “mail” is used to encompass items delivered by the United States Postal Service as well as other well known express shipping companies that deliver overnight letters, parcels, and other packages. In order to attract the attention of the mail recipient that particulate matter may be contained in a mail container, it would be a further benefit to have a mail container that included a quantity of clear, adhesive on only a portion of one or more of the transparent perimeter edge viewing windows so that the mail recipient or delivery person could immediately identify the existence of particulate matter contamination. Because persons unfamiliar with the mail container of the invention might not understand its operation, it would be a still further benefit if a quantity of clear, adhesive was deposited on only a portion of a number of in-line transparent perimeter edge viewing windows wherein each window had adhesive shaped in the shape of a letter such that should particulate contaminates become attached to the adhesive, a warning message, such as the word “DANGER” would be visible along a perimeter edge of the mail container.